Catalyst composition and process for oligomerization of ethylene to produce 1-hexene and/or 1-octene

1. A catalyst composition for the oligomerization of ethylene to produce 1-hexene or 1-octene, the catalyst composition comprising:

a chromium compound;

an NPNPN ligand of the formula

(R 1 )(R 2 )N—P(R 3 )—N(R 4 )—P(R 5 )—N(R 6 )(R 7 )

wherein R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 are each independently hydrogen, halogen, amino, trimethylsilyl, C 1 -C 20 hydrocarbyl, phenyl, C 6 -C 20 aryl, or C 6 -C 20 alkyl-substituted phenyl; and

an activator or co-catalyst.

2. The catalyst composition of claim 1 , wherein the chromium compound comprises an organic salt, an inorganic salt, a coordination complex, or an organometallic complex of Cr(0) or Cr(III).

3. The catalyst composition of claim 1 , wherein the chromium compound comprises Cr(III)acetylacetonate, Cr(III)octanoate, CrCl 3 (tetrahydrofuran) 3 , Cr(III)-2-ethylhexanoate, chromium hexacarbonyl, Cr(III)chloride, benzene(tricarbonyl)-chromium, or a combination comprising at least one of the foregoing.

4. The catalyst composition of claim 1 , wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , and R 7 are each independently hydrogen, chloro, methyl, ethyl, isopropyl, tert-butyl, n-hexyl, or phenyl.

5. The catalyst composition of claim 1 , wherein the activator or co-catalyst comprises trimethylaluminum, triethylaluminum, tri-isopropylaluminum, tri-isobutylaluminum, diethylaluminum chloride, ethylaluminum sesquichloride, ethylaluminum dichloride, methylaluminoxane, or a combination comprising at least one of the foregoing.

6. The catalyst composition of claim 1 , wherein the ligand comprises

Et(Me)N—P(Ph)-N(Me)-P(Ph)-N(Me)Et,

C 6 H 11 (Me)N—P(Ph)-N(Me)-P(Ph)-N(Me)C 6 H 11 ,

i Pr(Me)N—P(Ph)-N(Me)-P(Ph)-N(Me) i Pr,

H( t Bu)N—P(Ph)-N(Me)-P(Ph)-N( t Bu)H,

(C 6 H 11 ) 2 N—P(Ph)-N(Me)-P(Ph)-N(C 6 H 11 ) 2 ,

i Pr(Ph)N—P(Ph)-N(Me)-P(Ph)-N(Ph) i Pr,

H(Ph)N—P(Ph)-N(Me)-P(Ph)-N(Ph)H,

H( i Pr)N—P(Ph)-N( i Pr)—P(Ph)-N( i Pr)H,

Et(Me)N—P(Ph)-N(C 6 H 11 )—P(Ph)-N(Me)Et,

Et(Me)N—P(Me)-N(Me)-P(Me)-N(Me)Et,

or a combination comprising at least one of the foregoing.

7. The catalyst composition of claim 1 , further comprising a solvent.

8. The catalyst composition of claim 7 , wherein the solvent is toluene, chlorobenzene, o-dichlorobenzene, bromobenzene, chlorocyclohexane, chlorohexane, multiple halogenated aromatic mixtures, or a combination comprising at least one of the foregoing.

9. The catalyst composition of claim 1 , wherein the concentration of the chromium compound is from about 0.01 to about 10 mmol/l.

10. The catalyst composition of claim 1 , wherein the molar ligand/Cr ratio is from about 1.0 to about 5.0.

11. The catalyst composition of claim 1 , wherein the molar Al/Cr ratio is from about 1 to about 500.

12. The catalyst composition of claim 1 , wherein the C 1 -C 20 hydrocarbyl is straight-chain or branched C 1 -C 10 alkyl.

13. The catalyst composition of claim 1 , wherein the activator or co-catalyst comprises modified methylaluminoxane.

14. A catalyst composition for the oligomerization of ethylene to produce 1-hexene or 1-octene, the catalyst composition comprising:

Cr(III)acetylacetonate,

Et(Me)N—P(Ph)-N(Me)-P(Ph)-N(Me)Et; and

MMAO-3A.

15. A process for the oligomerization of ethylene, comprising

contacting ethylene with the catalyst composition of claim 1 under ethylene oligomerization conditions effective to produce 1-hexene or 1-octene.

16. The process of claim 15 , wherein the contacting is at a pressure of from 10 to 100 bar.

17. The process of claim 15 , wherein the contacting is at a temperature of from 30° C. to 100° C.

18. The process of claim 15 , wherein the mean residence time is from 10 minutes to 20 hours.

19. The process of claim 15 , wherein a weight ratio of 1-hexene to 1-octene is in the range from 0.1 to 10.

20. An ethylene oligomerization reaction producing 1-hexene and 1-octene, wherein the selectivity for 1-hexene or 1-octene is at least 90%, comprising a chromium-based catalytic system, wherein the chromium-based system comprises: a chromium compound; an NPNPN ligand of the formula

(R 1 )(R 2 )N—P(R 3 )—N(R 4 )—P(R 5 )—N(R 6 )(R 7 )

wherein R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 are each independently hydrogen, halogen, amino, trimethylsilyl, C 1 -C 20 hydrocarbyl, phenyl, C 6 -C 20 aryl, C 6 -C 20 alkyl-substituted phenyl, optionally wherein the ligand is a cyclic derivative wherein at least one of the P or N atoms of the ligand is a member of a ring system, or any cyclic derivative thereof wherein at least one of the P or N atoms of the NPNPN ligand is a member of a ring system, the ring system being formed from one or more constituent compounds of the ligand by substitution; and an activator or co-catalyst.